Method for cracking oils in vapor phase



METHOD FOR CRACKING OILS IN VAPOR PHASE Original Filed Dec. 1, 1928 5Sheets-Sheet 1 m I l H II INVENTOR PERCY C. KEITHJR.

ATTORNEY Sheeta-Sheet 2 P. C. KEITH, JR

Original Filed Dec. 1, 1928 METHOD FOR CRACKING OILS IN VAPOR PHASE May31, 13..

INVENTOR PERCY C. KEITHq/IP.

max Ao&l W

ATTORNEY P. c. KEITH, JR 2,119,331

METHOD FOR CRACKING OILS IN VAPOR PHASE Original Filed Dec. 1, 1928 5Skew-Sheet 3 w? A Q Q Q O OO OOYOO INVENTOR PERCY C. lfE/THJR.

ATTORN EY Patented May 31, 1938 METHOD son CRACKINGOILS 1N VAPOR.

PHASE Percy Keith, Jr., Peapack, N. J., assignor to Gasoline ProductsCompany,

Inc., Newark,

N. J., a corporation of Delaware Original application November 9,1933,Serial No.

697,283, which in turn is a divisiono'f Serial" No. 323,005, December 1,1928. Divided and this application December 6, 1935, Serial No.

This invention relates to the pyrogenesis of petroleum oils and is adivision of application Serial No. 697,283, filed November 9, 1933,which is in turn a division of application Serial No. 323,005,

filed December 1, 1928 which'has now'matured as Patent 1,972,149. Theinvention Will be fully' explained in the following. description andaccompanying drawings, in which:

Fig. 1 is a diagrammatic representation of a preferred embodiment ofapparatus in which my process may be carried out;

Fig. 2 is a diagrammatic representation of an alternative form;

Fig. 3 is a vertical section through a form of apparatus which may beemployed in conjunction with my process;

7 Fig. 4 is a cross section taken on the line 4 -4 of Fig. 3; and I vFig. 5 is a side elevation with parts in section of a form of apparatusemployed in conjunction with my process and with the apparatus shown inFigs. 3 and l.

p The pyrogenesis of petroleum oils forproduction of oils of lowerboiling point is carried out by heating crude petroleum, or such of itsdistillates as may economically be utilized in this manner, to crackingtemperatures With or without pressure. The fraction intermediate betweenkerosene and lubricating oils known as gas oil is frequently utilizedfor this purpose because of its lesser market value, although kerosene,lubricating oil fractions and fuel oils are also employed at times. Thefractions so employed are composed of an extended range of compounds asindicated by the range of molecular weights and boiling points. Theconglomerate of compounds is subjected to cracking conditions until acertain quantity of material falling within a desired boiling range isproduced. Simultaneously with the formation of this product, orproducts, materials are produced which do not fall within the desiredrange, for example, when cracking to produce a substantial proportion ofgasoline which is a product composed of a large variety of differenthydrocarbon compounds, there is simultaneous- 1y produced a quantity oftarry and coky materials. Some elements of a conglomerate stock, forreasons which will be given more fully later, require cracking to adegree less than others, and because of the fact that the stock as awhole is subjected to the same conditions the cracking reaction will becarried too far in the case of some of the constituents of the stock inorder to secure the desired quantity of material of a predeterminedboiling point range and with the re- 7 Claims. (01. l9649) sultantformation of compounds which do not fall within the said range or whichare deleterious to the operatiorigfor reasons which will be more'fullypointed out. The different cracking rates of some of the constituents ofthe stock tend to accentuate the condition referred to above. I

have discovered that a fundamental increase in the efficiency of thecracking process may be obtained by separating the cracking stock into aconditions have been established by such tests as to yield the samequantity of desired end products from a series'of segregated fractionsas is obtainable from cracking conglomerate stock the concomitant lossin gas and/or tarry or coky materials is diminished, or for anequivalent loss the'yield of the desired end products is relativelyincrease-d.

My process is applicable generally in the pyrogenesis of petroleum oilsto produce lower boiling point oils, as, for example, cracking toproduce either gas, gasoline, kerosene, gas oil or lubricating oil fromstocks of respectively higher boiling point.

In the ideal embodiment of my process the stock is segregated into aplurality of charging stocks of such character that under the conditionsof heat, time, and pressure imposed cracking of the various individualcompounds composing the fraction Will take place at substantially thesame rate. However, the limitations imposed by practice requiresegregation into a smaller number of stocks than in the ideal method andI'- therefore segregate into an appropriate number of charging stocksand subject each of such stocks to optimum conditions for the particularsegregate.

' I have discovered that in high molecular weight hydrocarbons ofstraight chain structure the initial scission on cracking frequentlyoccurs adjacent the center of themole'cular chain. In one-application inmy process I aim to obtain by cracking the-products of first scission'of the molecule, and I therefore prepare charging stocks which upontheir initial scission yield products which fall within the range ofphysical characteristics of the material desired to be obtained. Thus inthe case of gasoline I may proceed by dividing my charging stock into anumber of fractions each of which has a molecular weight substantiallytwice that of a constituent of gasoline, then by cracking the stocks tothe extent of one scission I obtain a number of products whose molecularweights fall within the range of molecular weights of the constituentsof gasoline. In cases in which the original charging stock containsconstituents so heavy that the products of their initial scission willnot fall within the range of physical characteristics of the desiredproducts, these constituents may be separated from the remainder of theoriginal charging stock, as by distillation, and treated in one of twoways; i. e. (1) by segregating them from one another as by distillationinto individual fractions and then subjecting each segregated fractionto such conditions as will produce from each segregated fraction aproduct which will yield, upon refractionation, products which may bedecomposed as above into gasoline constituents. This procedure enablesme to separate unsaturated constituents to a degree and to then subjectsuch fractions to appropriate treatment. (2) In view of the limitationsof practice I may subject the entire heavier conglomerate out tocracking conditions best suited to obtain the maximum yield of productswhich can be segregated into charging stocks of the nature described andcracked in the manner above set forth so as to yield gasolineconstituents.

Alternatively, I may prepare a number of fractions of charging stock,including some which cannot be converted by a single scission adjacentthe center of the molecule into products falling within the desiredrange, and subject each such fraction to the degree of time, temperatureand pressure necessary to its conversion into products of the desiredboiling point range. I may, however, in such cases crack each suchfraction to yield a cracked material having a position with respect tothe average molecular weight of the series of cracked materials obtainedwhich corresponds to the position held by the parent fraction withrespect to the other members of the parent series.

In addition to the foregoing I may make a further separation based onchemical characteristics. Thus, I may separate the original crackingstock into two fractions, one containing a preponderance of saturatesand the other containing a preponderance of aromatics and unsaturates,as, for example, by the application of selective treatment with liquidsulphur dioxide. These individual products may thereafter be separatedeach into products of different boiling point ranges to be separatelycracked. as hereinabove described. Alternatively, the fractions ofseparate boiling point ranges may be first prepared and each thereafterseparated into fractions of different chemical characteristics, as, forexample, by treatment with liquid sulphur dioxide.

In any event, where several fractions of the original charging stock areprepared, as by distillation, the decomposition products from theseveral fractions will preferably have average molecular weights whoseratio to each other is approximately the same as the ratio of molecularweights of the parent fractions. For example, in cracking gas oil toproduce gasoline the gas oil may be segregated by fractionation into aseries of several cuts, each of which has of constituents boiling withina different 50 F. range. The average molecular weights of thesefractions are in some ratio to their boiling points, the fraction ofrelatively high boiling point having the highest molecular weight. Incracking these individual fractions conditions are adjusted to produce aseries of cracked products having the same general relationship. Thus,the fractions of lower average molecular weight will have been crackedto produce a cracked material of lower average molecular weight thanwill have been produced from the parent fractions of relatively highermolecular weight. In this way the lighter constituents of the endproduct gasoline will have been predominantly produced from thosefractions of the cracking stock of lower molecular weight, whereas thosefractions of the gasoline of relatively higher molecular weight willhave been predominantly produced from the fractions of cracking stock ofrelatively higher molecular Weight.

I achieve a number of distinct advantages by this process, for example,the cracking is carried out on each of the individual cuts underconditions which may be predetermined in view of the rate ofdissociation of the particular stock to produce the optimum conversion,while the total number of dissociations or the degree of pyrogenesis toproduce any given yield of end product is relatively less than would benecessary with the indiscriminate cracking of a conglomerate stock, andthus the concomitant losses in gas and/ or tar or coke are greatlydiminished. A further distinct advantage is that polymerization to formproducts of a greater molecular weight than the parent stock does notoccur to the same degree as when cracking a conglomerate stock. It isunnecessary to carry the cracking reaction on some of the constituentsof the original stock to the point of forming polymers of a characterdeleterious to the operation of the process. Thus, in operating upon aconglomerate stock in the manner used at the present time it may beunavoidable to carry the cracking reaction to the point of third,fourth, fifth or higher scission in the case of some of the constituentsof the initial charge and to the scission of polymerized prod-' uctsformed therefrom in order to obtain the desired yield of the endproduct, whereas in my process I prefer to confine the reaction to theformation of the products of scission of a lower order. The scissions ofhigher order result in an increase in the products of decomposition, orpolymerization, which contributes to the formation of the products knownas tar and coke.

One of the preferred methods of operating my process is to crack eachindividual cut of the cracking stock to produce a cracked materialhaving an average molecular weight substantially half of that of theparent out, for example, ranging from 75 to 25% of the average molecularweight of the parent cut. In this way, toan ex- "40 be given to theformation of fixed gas.

View of the particular =stockor in View of the particularcharacteristics of .theproduct desired, as, for example, to produce agasoline having a certain definite proportion of material boiling withina certain predetermined range.

The particular method of cracking the individual stocks may be any oneof the methods at present employed or hereafter developed. I may, forexample, crack these individual cuts in either liquid or vapor phase orin, a combination of the two and under any degree of pressure. In apreferred embodiment of my invention, however, I subject the individualcuts to a vapor phase cracking of relatively short duration ranging, forexample, from the order of one second up to times of the order of fiveminutes, at temperatures which may range between 750 and 1500 F. and atpressures which may range from a few atmospheres to partialvacuum. Inthis way I am enabled to effect a carefully controlled dissociation ofthe individual stocks and accurately control the amount of dissociationapplied to each of these stocks so that a large proportion of theindividual cuts is subjected to a single dissocia- -tion, therebyautomatically throwing it into the boiling point range of the desiredend product with a minimum production of undesired products. -A furtheradvantage of this procedure that I have discovered is that owing to therelatively short times involved, the temperature range in which crackingis effected and the low specific volume of the gases in the crackingzone, the tendency to polymerization, or reformation of heavierproducts, is inhibitedthe efficiency of the operation is increased and Iam enabled to diminish the formation of tar and/or coke.

In determining the conditions under which individual cuts of the initialconglomerate charging stock are to be cracked consideration must Ibelieve that the theory at present held that fixedgas produced by acracking operation is substantial- 1y produced by the cracking of tar tocoke is mistaken and that in fact such fixed gas is substantiallyproduced by the cracking of constituentsfalling within the gasolinerange. I there- 'fore so select the conditions of operation in thepreferred form of my process as to prevent the cracking of such gasolineconstituents, as, for example, by removing them from the zone ofreaction as quickly as possible. In this respect my process is radicallydifferent from those at present practiced in which the products fallingwithin the gasoline range, or some of them, are held in the zone ofreaction-for considerable periods of time. In the processes in use atthe present time these products which are extant in the zone of reactionare either retained there by reason of the nature'of the apparatus whichdoes not permit of their evacuation immediately upon formation, or areretained there by reason of their so lution in liquid since they are incontact with large bodies of heavier liquid content in the system. Thiseifeot is considerably aggravated in many processes by the use ofpressure. It will be noted that in my improved process because of thenature of the apparatus and the charging stock used there issubstantially no liquid present in the system at anytime and theapparatus is such that products falling within the gasoline range areremoved substantially as quickly as formed.

V The selection of the temperature bears a definite relation to the timeelement involved in the operationof the apparatus, "the more rapid theboiler sections at intermediate points.

evacuation of the products from the zone'of reaction the higher thetemperature whichmay be used, suflicient time being provided to permitthe reaction to take place. The effect'of removing the products from thezone of reaction is to arrest the reaction, and it may be desirable tocool immediately the products removed to prevent further reaction byreason of the contained heat.

My process will now be described with specific reference to theapparatus diagrammatically indicated in the drawings. Referringspecifically to Fig. 1 a cracking stock such as gas oil is passedthrough the tubular heater l, surrounded by the refractory setting 2,and heated by means of a burner such as 3 communicating with the settingthrough the port A. Any alternative means of heating this stock to atemperature of complete or partial vaporization may be employed, such asa heat exchanger or a still. The partly vaporized cracking stock isdelivered through the pipe 5 into the fractionating column 6. Thiscolumn may be suitably insulated and provided with-a number ofrectifying devices suchas the customary transverse partitions carryingdown flow pipes and vapor contacting devices, not shown.

The design of this column is not a feature of the invention and anycolumn or corresponding device which is appropriately designed toseparate petroleum oil into a number of fractions by rectification maybe alternatively employed. Provision is made for taking off an overheadcut in vapor phase from the column by means of the vapor outlet 1 and anumber of side cuts (ordinarily in liquid phase, but which may be in thevapor phase) from the side outlets 8, 9, ill, I I, I2,

to the top or intermediate points and with aheatingcoil adjacent to thebottom or withremodifications will be incorporated to the degreenecessary to obtain the desired separation of the individual fractions.outlets l to l5, inclusive, are, in View of the necessities of practice,relatively close out fractions having, for example, 90% of constituentsboiling within a 50 F. range, and while these ranges to some extentoverlap, the cuts repre-' sent a complete series of charging stocks,each of which approaches, within the limits of commercialpracticability, an ideal charging stock as above defined. This series ofcuts has a range of boiling points and corresponding molecular weightswhich increases throughout the series. These various cuts are passed toindividual crackers through control apparatuses Hi to 23 inclusive whichwill be hereinafter more fully described, and from the controlapparatuses the cuts pass respectively to the individual crackingapparatuses which have been diagrammatically indicated by the numerals24 to 3|, inclusive. I may employ any form of cracking apparatus, suchas stills which may be adapted to operate under pressure or tubularcrackers with or without reaction chambers or tubular stills operated inthe vapor phase. In any event, the cracking is carried out underconditions which may be ,ascertained in advance by tests to besuited tothe The cuts taken off through All such individual out. Preferably, whenoperating to make gasoline the individual cuts are cracked to such anextent that the average molecular weight of the cracked materialproduced from an individual cut ranges from 25 to of that of the parentfraction. I obtain in this way a series of cracked products withserially larger molecular weights corresponding in order to themolecular weights of the original fractions of cracking stock. Thedesired end product is therefore obtained by the selective cracking ofpreferred stocks and with less actual molecular disruptions andrecombinations than would be incidental to handling a cracking stock asa conglomerate. For convenience all of the cracked materials dischargedfrom the crackers 24 to 3|, inclusive, through outlets 32 to 39,inclusive, may be conducted by means of the manifold 40 into therectifying column 4| which is of suitable construction to permit theseparation thereof into the desired end product, as, for example,gasoline which may be taken off in vapor phase, if desired, through theoutlet 42, and a number of side cuts taken off through the side outlets43 to 50, inclusive. These side cuts taken off through the outlets 43 to59, inclusive, are preferably fractionated so that of the constituentsof each cut boil within a range of 50 F. and will be hereinafter morefully considered. The column 6 may be operated under any pressure atwhich appropriate fractionation may be secured, and for purposes of heateconomy, is preferably operated under a pressure in excess ofatmospheric, say, for example, a pressure not exceeding pounds persquare inch. I achieve in this way the additional advantage that thecuts taken off from the outlets 8 to l5, inclusive, may, in this manner,be supplied by virtue of their initial pressure to the respectivecracking apparatuses 24 to 3|, inclusive. The column 4| may be operatedunder pressure preferably less than that obtaining in column 6 so thatthe progress of material through the entire system is effected by virtueof the initial pressure obtaining in column 6. The side cuts from column5 fall within the gas oil range and are such as may, to a large extent,be converted into constituents boiling within the gasoline range,particularly where the cracking is so controlled as to produce moleculardisruptions occurring at or near the mid-point of the molecule.

The plant illustrated is only an approach to the ideal and somepolymerization may occur to products whose molecular weight is higherthan those taken off through the side outlets B to l5, inclusive, ofcolumn 6. Such polymerized products are preferably separately processedas outlined in the preferred manner of processing the cut withdrawnthrough l5a, but for commercial reasons may be removed from column 4|through the side outlets 5| and diverted through pipe |5a to pipe |5b tobe combined with and processed with the products withdrawn from column 6through outlet l5a.

The materials delivered through the pipe |5b represent materials whichcannot be converted into constituents of the gasoline series by a singledisruption adjacent the center of the molecule and, while I maysegregate these bottoms by fractionation in the manner described andthereafter crack selectively the individual components and thenrefractionate and then recrack the individual components falling withinthe gas oil range to gasoline range, I find it suflicient to subjectthese components to a mild cracking by forcing the same through thetubular heater 52 surrounded, for example, by the refractory setting 53heated through the port 54 by means of the burner 55. The crackingeffected in the heater 52 is not intended to convert the stock treatedtherein predominantly to gasoline, but rather to convert a substantialproportion of the stock into stocks having molecular weightsapproximating those removed from column 6 through the side outlets 8 tol5, inclusive. There is, of course, the incidental production of a smallquantity of gasoline where the operation is not accurately controlled.The stock cracked in this manner is delivered through the outlet 56 intothe rectifying column 51, which may be of any suitable construction, inwhich it is fractionated to form an overhead distillate, for example,taken off through the outlet 58 which may consist of gasoline and aseries of intermediate cuts taken off through the side outlets 59 to 66,inclusive, which are preferably cut to have 90% constituents boilingwithin a range of 50 F. These constituents boiling within the keroseneand gas oil ranges are such as may to a large extent be converted intoconstituents of gasoline by a single disruption occurring at or adjacentthe mid-point of the individual molecule. Any heavy ends may be takenoff through the side outlet 68, and, while they are preferably handledby separation and cracking of the individual segregates, as aboveoutlined, I find it suflicient in commercial practice to carry thesecompounds by means of the pipe 69 back into the inlet side of thetubular heater 50 for a second cracking operation. Any tarry productscollecting in the base of the towers 4|, 5'! and 9| are withdrawn bymeans of bottom outlets 50a, 10 and Illa, and diverted from the system.The products obtained from the side outlets 59 and 66 inclusive,represent products which have been cracked and separated into productshaving .a molecular weight approximating those removed from the sideoutlets on column 6. As segregates they are passed through the controlapparatuses diagrammatically indicated by the numerals H to 18,inclusive, discharging into cracking apparatuses fll to 88,inclusive,which may be of any suitable construction, although they are preferablyof the type hereinafter described. The cuts obtained from tower 4| fromthe side outlets 43 to 50, inclusive, are cuts which have been subjectedto cracking and subsequent fractionation. These preferably will becracked in the same manner as cuts 8 to I5, inclusive, derived fromtower 6, but for commercial reasons they may be blended with cuts 59 to66, inclusive, and passed through the crackers 8| to 88, inclusive. Inthe ideal embodiment of my process all polymerized cuts, even of thesame molecular weight as the cuts 8 to l5, inclusive, will be treatedseparately. This is desirable for two reasons, the first being that thedissociation speed of these polymers may be different than those of 8 tol5, inclusive, and further, because I have discovered that the presenceof polymerized cuts in contact with undecomposed cuts will enhance theformation of tar.

The cracking accomplished in these cracking apparatuses is conductedunder conditions ascertained by test or experience to be best for theparticular cuts and may be so adjusted as to produce cracked materialhaving an average molecular weight ranging from 25 to 75% of the averagemolecular weight of the cut from which the cracked material is derived.In this way a series of cracked materials of serially larger averageterial. The cuts which have been cracked through apparatuses 8| to 88,inclusive, may be diverted through the common flow line 98 into therectifying column -9I which may be of any suitable design. From thisrectifying column gasolinejmay'be removed through outlet 92.

Fromthe side of column 9| a series of cuts, shown ,as 93 to 88a,inclusive, may be withdrawn and because of their small quantity may bediverted through crackers 8| to 88, inclusive. It will be understoodthat if the pressure in, or the location of, the tower 9I is not such asto cause liquid to flow through the lines 93 to 99a, inclusive, into thelines leading to the crackers 8I to 88, inclusive, suitable pumps andcheck valves or other well-known apparatus may be employed for effectingthis purpose.

- The cut I08 may be diverted back to the tubular heater as in the caseof cut 5| as is the case likewise with cut 68 from column 51. Thecut 68differs from cuts I 00 and 5| in that it represents to a large extentproducts which have not been converted into those ofthe desiredmolecular weight, whereas cuts 5I and I00 are substantially productswhich have been formed by polymerization since the plant shown is onlyan approach to the ideal. For the same reason: as before outlined, tarrymatter may be removed through line lIlUa.

Referring specifically to Fig. 2 which is the diagrammatic elevation ofapparatus'adapted to processing crude oil or other petroleum oilscontaining constituents of higher boiling point than gasoline. Thecharging stock is passed through the tubular heater I surrounded by thesuitable refractory setting 2, heated by means of the burnerdiagrammatically indicated at 3, communicating with the setting throughthe port 4. The crude oil may be heated in heater I to a temperature ofsubstantially complete or partial vaporization and is thereafterdischarged through pipe 5 into the rectifying column 6. In the eventthat it is desired to produce a quantity of gas oil or cracking materialin addition to that normally occurring from the crude, conditions in thetubular heater I may be adjusted toproduce a cracking effect, preferablyof a moderate char a'cter, to convert heavier materials to aconsiderable extent into-,,products such as kerosene and gas oil, whichproducts are in turn susceptible to being converted into gasoline by aminimum number ofmolecular disruptions. This operation is not, ofcourse, conducted under the ideal cracking conditions which Ihavehereinabove described, but is utilized :only as a matter ofexpediency. The rectifyingcolumn 6 maybe of any suitable type. Provisionmay, for example, be made-to take an overhead cut of gasoline by meansof the vapor outlet I and a series of side cuts from the outlets 8 toI5, inclusive, and H5, to H8, inclusive. It wi1l,.of course, beunderstood that any alternativenumbercof side cuts may be employed, thedesign in any case being determined by the character of the stock .to betreated and the number of. side cuts which it is desired to make.vAssuming that cuts such as kerosene and gas oil are taken off from theside outlets 8 to I5, inclusive, these are preferably fairly closelyfractionated so that 90% of the total constituents of each cut will boilWithin a range of say 50 F. Products evolved from the tower 6 which areheavier than gas oil, or so heavy that they cannot be converted intogasoline to a large extent by a single disrup tion adjacent themid-portion of the molecule, may be takenoff from the column 6 by meansof the side outlets II5. to H8, inclusive, combined in the manifold 5aand thereafter. treated in the same manner as the products obtained fromthe outlet 55a of Fig. 1. Any heavy residue resulting during theoperation may be diverted from the system by means of the outlet I20.

The several side cuts taken from column 8 through the side outlets 8 toI5, inclusive, may be handled in the identical manner as the side cutstaken from column 6 of Fig. 1 through the side outlets 8 to I 5,inclusive, and inasmuch as the product taken from column 6 through theside outlets H5 to H6, inclusive, is handled in the identical manner asthe products taken from the column 5 in Fig. 1 through the pipe I5a, thesubsequent progress of these materials may be ascertained by referenceto the previous description relating to Fig. l and need not be morefully illustrated or described. Referring specifically to Figs. 3 and 4,the form of cracking apparatus which I prefer to employ for cracking theindividual closely fractionated cuts which have been described from,time to time is detailed, which apparatus has been designated forexample by numerals 24 to 3I, inclusive, and 8| to 88, inclusive. Thisapparatus consists of a refractory setting I56 andmay be heated throughthe port I5I by means of. the burner diagrammatically indicated as I52.A baffle wall such as I53 may be provided and a down draft section I54communicating with a stack I55. The tubular heaters I56 and I51 in thedown draft section may comprise a number of tubes through which oil maycirculate by means of inlets and outlets I58, I59, I68,

IBI, respectively, and sections of this character may be utilized forheating or cracking the cuts of relatively wide boiling pointcorresponding to the operations which have been previously described asconducted in tubular heaters I. and 52. The walls of the setting I50 arepreferably lined with a number of relatively short tubular heaters I62to I'll, inclusive, each of which is adapted to the circulation ofhydrocarbon materials by means of inlets and outlets such as Ififia andI65b, etc. These sections are relatively short being composed of only afew lengths of tubing adapted to be heated to a large extent by theradiant products of combustion evolved. In operation I prefer tomaintain these heaters I62 to III, inelusive, at temperaturesintermediate between 750 and 1500 F. and to conduct cracking operationstherein at relatively low pressures ranging from a few atmospheres tosubatmospheric. The total time of heating of the hydrocarbon gases atthese temperatures is preferably limited to a period ranging from onesecond up to the order of five minutes, which conditions I find to favora symmetrical dissociation which isamenable to control with asimultaneous formation of a relatively small quantity of the products ofre-association or polymerization. In vapor phase cracking apparatus,such as that shown, I may admix with the petroleum oil undergoingcracking in the vapor phase a material to limit the formation ofpolymers. I have discovered the formation of deleteriously affect thecracking reaction, will be hereinafter referred to as diluent gases. Thecracked and heated hydrocarbons delivered through the respective outletsof coils 862 to ill, inclusive, are preferably quenched by cooling themimmediately either by contact with a liquid or a vapor at temperaturebelow cracking, for example, by contact with steam or by conducting themagainst relatively cool metal surfaces, for example, through arelatively cool large eX- changer. I am thus enabled to control theextent to which the reaction is permitted to proceed and thus determinethe constitution of the product. The combination, rectification andsubsequent disposition of these products has been hereinabove described.

Referring specifically to Fig. 5, this is a diagrammatic representationof control apparatus which has been indicated by the numerals IE to 23,inclusive, and H to '18, inclusive. This apparatus comprises the sideoutlet, such as 8, carrying a fraction from any one of the rectifyingcolumns hereinabove described, discharging into cracking apparatus suchas diagrammatically indicated by the numeral 26. A cooling coil such as200 is connected into the outlet 8, preferably adjacent the under sidethereof. This coil, controlled by the valve 29 I, discharges into thepipe 8 at a point below its origin. The coil 2% may be surrounded by areceptacle, such as 262, through which a cooling fluid is circulated bymeans of inlets and outlets, such as 203 and 264, respectively, so thatany petroleum oil, either in liquid or vapor form, passing through thecoil 200 is automatically cooled and discharged in cooled condition backinto pipe 8. By manipulation of the valve 21!! the amount of cooledmaterial which is reintroduced into the pipe 8 may be carefullycontrolled, and in this way the temperature of the products passing intothe cracking apparatus 24 may be controlled, and hence the temperatureof the products discharged from the cracking apparatus 24 may becorrespondingly controlled. The form of apparatus which I have justdescribed is particularly adapted to the close control of vapor phasecracking, which I prefer to conduct in apparatus such as 24 and to whichI prefer to subject the various fractions into which I separate myoriginal cracking stock.

I claim:

1. The process of treating hydrocarbon oil which comprises introducinghighly heated oil into a separating zone wherein separation of the oilinto vapors and liquid residue occurs as a result of its contained heat,fractionating in a first fractionating zone vapors separated in saidfirst separating zone to form an intermediate condensate, removingfractionated vapors from said first fractionating zone and condensingthem as a desired product, subjecting such intermediate condensate tocracking temperature to effect conversion into lower boiling products,fractionating resultant products of said cracking in a secondfractionating zone to form an intermediate condensate, withdrawing saidliquid residue from said separating zone and passing it through aheating zone in a stream of restricted crosssectional area, whereby saidoil is raised to a cracking temperature and subjected to conversion,introducing the resulting cracked products into a second separating zonewherein vapors separate from residue, fractionating in a thirdfractionating zone vapors separated in said second separating zone toform an intermediate condensate, removing the fractionated vapors andcondensing them as a desired product, mixing intermediate condensateremoved from said second fractionating zone with intermediate condensateremoved from said third fractionating zone and passing the mixture soobtained through a second heating zone wherein it is raised to acracking temperature and subjected to conversion, introducing theresulting cracked products into a separating zone wherein vaporsseparate from residue, and fractionating vapors so obtained to form anadditional quantity of final desired products.

2. The process of treating hydrocarbon oil which comprises introducinghighly heated oil into a first separating zone to cause separationthereof into vapors and a liquid residue, fractionating in a firstfractionating zone vapors separated in said first separating zone toform an intermediate condensate, removing vapors from said firstfractionating zone and condensing them as a final desired product,removing said liquid residue and passing it through a first heating zonewherein it is raised to a cracking tempera ture and subjected toconversion, introducing the resulting cracked products into a secondseparating zone wherein separation thereof into vapors and a liquidresidue occurs, removing said liquid residue last mentioned,fractionating said vapors in a second fractionating zone to form anintermediate condensate, passing the last named in termediate condensatethrough a second heating zone wherein it is raised to a cracking temperature and subjected to conversion, introducing the resulting crackedproducts into a third separating zone wherein vapors separate fromliquid residue, fractionating said vapors lastmentioned in a thirdfractionating zone to form an intermediate condensate and a relativeiyheavy condensate, combining said heavy condensate with the liquidresidue removed from said first separating zone for passage through saidfirst heating zone, and removing fractionated vapors from said thirdfractionating zone and condensing them to form an additional quantity offinal desired products.

3. The process of treating hydrocarbon oil which comprises passingrelatively heavy oil through a first heating zone, introducing resultinghighly heated oil into a first separating zone wherein vapors separatefrom liquid residue, fractionating vapors so obtained in a firstfractionating zone to form an intermediate condensate, removing thefractionated vapors and condensing them as a final desired product,removing liquid residue from said first separating zone and passing itthrough a second heating zone in a stream of restricted cross-sectionalarea, wherein it is raised to a cracking temperature and subjected toconversion, introducing the resulting cracked products into a secondseparating zone wherein vapors separate from residue, fractionatingresulting vapors in a second fractionating zone, removing thefractionated vapors and condensing them as a desired pro-duct, removingintermediate condensate collected in said first fractionating zone andpassing it through a third heating zone in a stream of restrictedcrosssectional area wherein it is raised to a cracking temperature andsubjected to conversion, introducing the resulting cracked products intoa third separating zone wherein vapors separate from residue,fractionating vapors so obtained in a third fractionating zone to form arelatively heavy condensate, removing fractionated vapors from saidthird fractionating zone and condensing them as a desired product, andremoving heavy condensate from said third fractionating zone andcombining it with liquid residue removed from said first separating zonefor passage through said second heating zone.

l. A process in accordance with claim 3 wherein an intermediatecondensate is formed in both the said second fractionating zone and saidthird fractionating zone, said condensates are removed and passed as amixture through a fourth heating zone wherein the mixture is raised to acracking temperature and subjected to conversion, the resulting crackedproducts are introduced into a fourth separating zone wherein vaporsseparate from residue, and vapors so obtained are fractionated to forman additional quantity of final desired products.

5. The process of treating hydrocarbon oil which comprises passing crudeoil through a first heating zone wherein it is raised to a crackingtemperature and subjected to conversion, introducing the resultingcracked products into a first separating zone wherein vapors separatefrom liquid residue, fractionating vapors so obtained in said firstfractionating zone to forman intermediate condensate, removing thefractionated vapors and condensing them to form a final desired product,removing liquid residue from said first separating zone and passing itthrough a second heating zone wherein it is raised to a crackingtemperature and subjected to conversion, introducing the resultingcracked products into a second separating zone wherein vapors separatefrom residue, fractionating vapors so obtained in a second fractionatingzone to form an intermediate condensate and a heavier condensate,removing the fractionated vapors from said second fractionating zone andcondensing them to form an additional quality of final desired products,removing said heavier condensate and combining it with the liquidresidue removed from said first separating zone for passage through saidsecond heating zone, removing intermediate condensate from said firstfractionating zone and passing it through a third heating zone whereinit is raised to a cracking temperature and subjected to conversion,introducing the re sulting cracked products into a third separating zonewherein vapors separate from residue, fractionating vapors so obtainedin a third fractionating zone to form intermediate condensate, removingfractionated vapors from said third fractionating zone and condensingthem to form an additional quantity of final desired products, re-

moving intermediate condensate from said second and from said thirdfractionating zones and passing them as a mixture through a fourthheating zone wherein the mixture is raised to a cracking temperature andsubjected to conversion, introducing the resulting cracked products intoa fourth separating zone wherein vapors separate from residue, andfractionating vapors so obtained to form an additional quantity of finaldesired products.

6. The process of treating hydrocarbon oil which comprises introducinghighly heated oil into a first separating zone to cause separationthereof into vapors and a liquid residue, fractionating in a firstfractionating zone vapors separated in said first separating zone toform a final desired product, removing said liquid residue and passingit through a first heating zone wherein it is raised to a crackingtemperature and subjected to conversion, introducing the resultingcracked products into a second separating zone wherein separationthereof into vapors and a liquid residue occurs, fractionating saidvapors in a second fractionating zone to form an intermediatecondensate, passing the last named intermediate condensate through asecond heating zone wherein it is raised to a cracking temperature andsubjected to conversion, introducing the resulting cracked products intoa third separating zone wherein vapors separate from residue,fractionating said vapors last-mentioned in a third fractionating zoneto form an intermediate condensate and a relatively heavy condensate,combining said intermediate condensate with said intermediate condensatefrom the second fractionating zone for passage through said secondheating zone, combining said heavy condensate with the liquid residueremoved from said first separating zone for passage through said firstheating zone, and removing fractionated vapors from said thirdfractionating zone and condensing them to form an additional quantity offinal desired products.

'7. The process of treating hydrocarbon oil which comprises introducingheated oil into a first separating zone wherein separation of the oilinto vapors and liquid residue occurs, fractionating in a firstfractionating zone vapors separated in said first separating zone toform a condensate, passing said liquid residue and said condensatethrough separate cracking zones wherein they are heated at crackingtemperature and subjected to conversion, subjecting the resultingproductsof the cracking of both said liquid residue and said condensateto fractionation, separate and apart from said first separating andfractionating zones, passing a resultant condensate through a separatecracking zone wherein it is heated at a cracking temperature andsubjected to conversion, separately subjecting the resulting crackedproducts to fractionation to form a final desired light distillate and aheavy reflux condensate and combining said heavy reflux condensate withsaid liquid residue for cracking therewith.

PERCY C. KEITH, JR.

